I unlocked the bootloader and rooted the device already like this: How to unlock and root a Sony Ericsson Xperia Ray ST18i with 4.1.B.1.13 But How can I install a custom Rom now on the device?
I guess I have to enter the recovery menu for it?
I tried this, but it doesen't work:
press the volume down key a few times when your phone boots up. The sony logo brightens at one point, press during that time